At rapid heart rates
a. systole and diastole shorten equally
b. systole stays almost constant, but diastole shortens
c. systole lengthens and diastole shortens
d. diastole lengthens and systole shortens
e. none of the above occur
B
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The pulmonary trunk receives blood from the right ventricle and conducts it toward the lung. The pulmonary trunk is a(n)
A. artery. B. capillary. C. vein.
Which of the following does NOT affect the tension that can be developed by a muscle fiber?
a. the number of motor units recruited b. the frequency of action potentials conducted by the motor neuron c. the length of the fiber at the onset of contraction d. diameter of the muscle fiber e. All of these affect tension development by a muscle fiber.
Human body cells have many functions, including
A. producing new cells. B. providing for defense. C. lining surfaces. D. making connections. E. All of the choices are correct.
Three adjacent nucleotides in mRNA are called a
A. pre-mRNA. B. gene. C. codon. D. ribosomal RNA (rRNA). E. proenzyme.